The night sky
in May

Want to know what's up in the sky tonight? Our night sky chart will
provide you with the information you need to locate the brightest planets,
stars and deep-sky objects ...

During early May, the Earth passes through a debris trail left by comet
Halley. This results in a meteor shower is called the Eta Aquarids. They are so
called because the meteors appear to come from part of the constellation of
Aquarius. (In October we pass through another section of Halley’s debris path
in a shower called the Orionids.)

At their peak on May 5, the Eta Aquarids may produce up to 30 meteors per
hour.

This month’s chart shows the night sky
looking South in mid May at 2300. (click on image for larger view)

The Stars and Constellations

May is a great month to enjoy the night sky because the weather is so much
better (hmmm, we’ll see!). Soon after sunset we see a sky that is moving into
its ‘Summer phase’. If you stay outside a few hours past sunset you will
get a preview of our summer stars and constellations.

Rising from the eastern horizon, about an hour after sunset is the brilliant
star Vega. With a magnitude zero (0.0), is a real treat on its very own. It’s
50 times more luminous as the Sun and only 26 light-years away so it’s very
bright in our night sky.

In 1983 a cloud of cool material orbiting Vega was detected. This was
interpreted as a disk of sub-planetary size materials – like asteroids and
comets – orbiting the star. We believe that our Solar System started in this
way; as a disk of condensing materials that eventually accumulated by gravity
into planets. In the 1990s instruments mapped the shape of the material
surrounding Vega (and two other stars, Fomalhaut and Beta Pictoris). The
results showed that there are localized concentrations of materials in some
places and gaps in other parts. Some astronomers interpret this as evidence of
planet formation. So. it’s possible that at this very moment, planets are
being created around Vega.

Opposite Vega but still in Lyra is the Ring Nebula (M57). Not so long ago an
old star used to sit in this part of Lyra. It eventually ran out of nuclear
fuel and underwent a series of pulsations, eventually throwing off its outer
layers in a violent explosion. The nebula’s ‘ring’ is actually, in
simplistic terms, material ejected from the dying star. Its ring appearance is
just a line-of-sight effect. When nebula like these were first discovered,
hundreds of years ago, it was thought that the ring was due to condensing, not
expanding, material. This is why they were so-called ‘planetary nebula’.
Nothing could be further from the truth! A planetary nebula is not the sign of
planet formation. It’s the sign of a recently dead star. Indeed, any planets
that orbited close to the star, were probably annihilated.

The corpse left behind, in the center of the explosion, is a white dwarf.
These stars are very dense. A teaspoon of white dwarf material weighs a ton –
literally – that’s about a thousand kilograms per cubic centimeter. It’s
impossible to squeeze atoms that tightly without destroying their atomic
structure. Every atom in the white dwarf is transformed into an unusual state
of matter called degenerate matter – a tight mass of nuclei and electrons
with no real atomic structure. There’s nothing on Earth quite like it. The
light given off by a white dwarf is the remnant energy leftover from its former
life as a proper nuclear-fusing star. White dwarfs no longer undergo nuclear
fusion.

The Ring Nebula is too dim for most low-power binoculars but within the
range of a good telescope. It’s a great find for amateur astronomers so, if
you have a telescope, give it a try.

At 2230 in mid-May the bright star Arcturus is almost due South. If you have
trouble finding it use the handle of the Plough to trace an arcing line 30
degrees away from it, taking us on to Arcturus. The star is unmistakable as it
is the brightest object in that region of the sky.

Arcturus is the Alpha (meaning the brightest) star of the constellation
Bootes. It is a giant star, twice as massive and 215 times as bright as the
Sun. It takes 37 years for its light to reach us, so when we gaze at it,
we’re seeing the star as it looked 37 years ago. Once you have found it, you
will notice that it forms the point of a pattern of stars resembling a kite.

Ancient astronomers had measured the position of Arcturus for nearly 2,000
years, which gave Edmond Halley enough data, in 1718, to discover that it was
slowly moving against the background stars of its constellation. Before this
discovery of proper motion, the stars were thought to be permanently fixed in
the sky. Today we know that all stars move, but Arcturus moves much faster than
most—about the width of the full moon every 800 years.

Locate the two middle stars within the kite shape. Using binoculars trace a
line in the direction of four o’clock (from the right-hand star) for 11
degrees until you arrive at a smudge of fuzzy light. This is the globular
cluster M3. It contains about 500 000 stars. M3 is host to more known variable
stars than any other globular cluster. It was Messier’s first original
discovery. With the naked eye, it is difficult to separate M3 from a nearby
orange sixth magnitude star. With a telescope and moderate power this cluster
takes on a 3-dimensional quality with many stars resolved around the edges and
across the central halo.

In history …

On the first night of May, 1949 Gerard Kuiper discovered Nereid, Neptune’s
second largest Moon. (Until Neptune was visited by the Voyager spacecraft, it
was thought that it had only two moons) Subsequent observations of Nereid
showed it had a highly eccentric orbit – it’s distance from Neptune varies
from 1.3 to 9.7 billion kilometers.

On May 28, 1959 Able and Baker complete a sub-orbital flight to become the
first primates in space.

Alan Shepard became the first American in space on May 5, 1961. His 15
minute sub-orbital flight in the Mercury spacecraft Freedom 7 put him in second
place to the Russian Yuri Gagarin, who had orbited the Earth (one orbit) three
weeks earlier.

Regardless, Shepard’s flight made the space race a two nation race …
Sixteen days later, on May 21, President John F. Kennedy, speaking before a
joint session of Congress upped the ante by declaring, ‘I believe this nation
should commit itself to achieving the goal, before this decade is out, of
landing a man on the Moon and returning him safely to the Earth.’ With that
sentence President Kennedy launched the most ambitious and far reaching science
and engineering program the world has ever seen.